The present invention generally relates to power hand tools, and more particularly, to power reciprocating tools.
Reciprocating tools that are motor driven, such as saber saws, larger reciprocating saws and the like are usually driven by electric motors that have a rotating output shaft. The rotating motion must be translated into reciprocating motion for moving a saw blade or the like in a reciprocating manner. While various types of mechanisms have been known in the art for translating the rotation motion into reciprocating motion, one common type of motion conversation mechanism is known as a wobble plate drive. A wobble plate drive shaft is typically connected to the motor through a gear arrangement to reduce the speed of rotation of the motor output shaft and the wobble plate drive causes a wobble arm to reciprocate in a path that is parallel to the motion of the saw blade or the like. The blade of a reciprocating saw is mounted in a blade clamping mechanism that is located at the end of a plunger, the other end of which is operatively connected to a wobble arm.
In some prior art wobble plate drives, the plunger has a rectangular or square cross-section that is located in a rectangular or square opening to restrain the plunger from twisting which would undesirably affect the angular orientation of a blade attached to the drive. While these noncircular cross-section plungers operate in a desirable manner, the noncircular cross-section increases the cost relative to a tubular plunger construction which is more desirable. However, there is a tendency of wobble plate drives to exert forces on the plunger which tend to cause it to rotate. It is highly desirable to prevent such rotation using a cost effective design that operates in a highly efficient manner.